Unfortunately we’re a nation of NIMBYs so not enough new housing is built and, as importantly, not enough good transport infrastructure is built to make long distance commutes viable.
This comment has really struck me and I keep coming back to it, because I think one of our big issues is that there is in the UK (and the anglophone world - there was a brilliant FT data story about this recently) that ever outward is the only way to achieve affordable housing. There's a deep bias towards houses and away from flats and a huge part of that has to be that by and large our record of building really liveable flats is extraordinarily poor - we either convert old houses cheaply and poorly or build stack 'em high developments.
Outside a few urban exceptions we don't have a lot of purpose built flats in that 'sweet spot' of 3-5 storeys high in the same way as a lot of cities on the continent mastered early and remain desirable for urban family living. Those areas that did high-quality flats well - mansion flats in London, the better tenements in Edinburgh and Glasgow - remain sought after. But no one is replicating them because there aren't financial incentives for developers to do this rather than high rise buildings with tiny rooms.
I was lucky enough to find myself in a flat share in a mansion flat when I first moved to London and it was amazing. Far better suited to family living than my current (very nice) suburban semi; it had gloriously big rooms - three massive bedrooms and two smaller box room sized ones, a good communal garden, storage in the cellar, energy efficient, small enough to know your neighbours and have a sense of community but big enough not to feel cramped. A really different way of thinking about higher-density living.
But instead we build ever outwards, and when we build upwards it's in ways that are less desirable for families and long-term living, and it further cements the bias towards houses being 'proper homes' and flats being second rate.